title: Sequence variation in group A Streptococcus pili and association of pilus backbone types with lancefield T serotypes.
abstract: BACKGROUND
  We previously reported that group A Streptococcus (GAS) pili are the T antigens described by Rebecca Lancefield. We also showed that these pili, constituted by backbone, ancillary 1, and ancillary 2 proteins, confer protection against GAS challenge in a mouse model.
  
  
  METHODS
  We evaluated pilus distribution and conservation by sequencing the subunits of 39 new GAS isolates and used immunoblot analysis and agglutination assays to define the specificity of T sera to pilus subunits.
  
  
  RESULTS
  GAS pili are encoded by 9 different islands within which backbone protein, ancillary protein 1, and ancillary protein 2 cluster in 15, 16, and 5 variants, respectively. Immunoblot and agglutination assays revealed that T type is determined by the backbone variant. This observation enabled us to set up a simple polymerase chain reaction assay to define the T type of GAS isolates.
  
  
  CONCLUSIONS
  We propose the use of a tee gene sequence typing, analogous to the emm gene typing, as a valuable molecular tool that could substitute for the serological T classification of GAS strains. From our sequence analysis and from recent epidemiological data, we estimate that a vaccine comprising a combination of 12 backbone variants would protect against > 90% of currently circulating strains.
authors.affiliation: Novartis Vaccines, Siena, Italy.
authors.forename: Fabiana
authors.initials: F
authors.lastname: Falugi
authors.forename: Chiara
authors.initials: C
authors.lastname: Zingaretti
authors.forename: Vittoria
authors.initials: V
authors.lastname: Pinto
authors.forename: Massimo
authors.initials: M
authors.lastname: Mariani
authors.forename: Laura
authors.initials: L
authors.lastname: Amodeo
authors.forename: Andrea G O
authors.initials: AG
authors.lastname: Manetti
authors.forename: Sabrina
authors.initials: S
authors.lastname: Capo
authors.forename: James M
authors.initials: JM
authors.lastname: Musser
authors.forename: Graziella
authors.initials: G
authors.lastname: Orefici
authors.forename: Immaculada
authors.initials: I
authors.lastname: Margarit
authors.forename: John L
authors.initials: JL
authors.lastname: Telford
authors.forename: Guido
authors.initials: G
authors.lastname: Grandi
authors.forename: Marirosa
authors.initials: M
authors.lastname: Mora
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D005798:Genes, Bacterial; D014644:Genetic Variation; D010802:Phylogeny; D013297:Streptococcus pyogenes / Q000145:classification / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins